This invention relates to an ultrasonic lipectomy probe and a method for manufacturing the probe. In addition, this invention relates to a lipectomy procedure or methodology which utilizes the probe.
Over the last 15 to 20 years, a procedure has been developed to remove unwanted fatty deposits from the human body in a hospital or clinical setting.
This procedure involves creating an incision in the skin, inserting an essentially hollow probe into the area between the dermis and underlying muscle. By connecting the other end of the probe to a vacuum source, the fat is effectively sucked from the area due to the differential pressure which exists across the probe's inlet orifice. By manipulating the probe in and out of the area, a large amount of fatty deposit may be removed and the existing bulges flattened, thereby improving the appearance of the person. Areas of the body which respond well to this procedure are the outer thighs ("saddlebags"), inner thighs, lower abdominal area, hip ("love handle") area and around the jowl areas of the face. The procedure has been dubbed "suction assisted lipectomy" or "liposuction" and it is currently a major source of revenue for the cosmetic surgery industry.
Although the esthetic benefits of this procedure are well documented, it is not without risk to the patient. Blood loss is a concern in some cases because the tissue is being ripped from the body and there is no differentiation between fat ripped from the body and there is no differentiation between fat and connective tissue or blood vessels. The physician must also use a great deal of force to push the probe in and out of the body, thereby inducing trauma to the surgical site or fatty deposit area. It is not uncommon for the patients to become severely bruised and tender in these areas for several days or even weeks after the procedure. Also, blood loss has been a problem in certain procedures, as the blood vessels are damaged by the thrusting of the probes and the trauma induced by the suctioning.
Another limitation using simple suction to remove the fat is that sculpturing of the area is not easily accomplished. Since the only tissue which is removed is that which is situated directly opposed to the inlet orifice, the probe creates channels or tunnels in the fat. By moving the probe in and out, a checkerboard or waffle pattern is created. The peaks of fat which are not removed then fold over and the area can be rendered fairly smooth as opposed to lumpy. However, the fringes of the deposit area cannot be feathered in to create a smooth transition between the liposuctioned area and the natural tissue immediately surrounding it. In some cases, a crater can be formed in the area where the fat was removed. This can be as unsightly as the original lump and is even more difficult to treat. Recently, several inventors have sought to activate the liposuction probes with high powered ultrasonic vibrations. See, for example, U.S. patent application Ser. No. 08/101,188, now U.S. Pat. No. 5,419,761.
In ultrasonic lipectomy procedures, the suction probe is connected to an electromechanical transducer of either magnetostrictive or electrostrictive design. Once the transducer is activated, longitudinal vibrations are set up in the probe and the distal end is turned into a vibrating wand which serves to liquefy the fat which comes into contact with it. The resultant fatty emulsion is then removed from the body much in the same way as the standard liposuction techniques, by way of a suction source and collection bottle. Several advantages are gained by the use of this equipment. First, the level of vacuum needed to remove the fat is substantially less than that needed for the standard liposuction procedure. Also, the probe will liquefy all of the tissue surrounding the distal end, which makes the probe easier to insert and retract from the body. This reduces the trauma to the patient, not to mention the reduction of effort needed by the surgeon. The benefit here is less fatigue on the part of the physician, thereby allowing him to be more alert and able to perform more procedures per day. In addition, less bleeding has been noted during trials of these devices, since ultrasound has been shown to have a cauterizing effect on small blood vessels. U.S. patent application Ser. No. 08/101,188, now U.S. Pat. No. 5,419,761 to Alliger et al. outlines several of these advantages.
Liposuction probes developed to date, whether for conventional vacuum assisted procedures or newer ultrasonically assisted ones, have basically been formed of tubular stainless steels or titanium. The distal ends of the probes have been closed or blunted to eliminate sharp corners which could cause injury when inserted into the body. In some cases, the inlet orifices have been disposed along a sidewall of the probe, so that the probe must be twisted during insertion to remove tissue evenly from the body cavity. The purpose of situating the orifice in this manner is to allow discrimination as to where the tissue is removed. For instance, if the orifice was pointed away from the underside of the dermis, the dermis would not be harmed by tissue fragmentation and removal.
While the tubular cannula designs discussed above are effective for use in conventional vacuum assisted liposuction procedures, they are not readily adaptable to the newer field of ultrasonically assisted liposuction. Here, other factors come into consideration when the design of the liposuction probe is undertaken. Since the probe is now being vibrated at ultrasonic frequencies (typically 16 to 60 kc), it is subjected to stresses and fatigue not encountered in the passive probes of current liposuction tooling. In addition, the ultrasonic probe must be designed to provide sufficient multiplication of the amplitude input provided by the transducer which drives it. Since straight cylindrical probes do not provide gain for ultrasonic vibrations, the probes must be driven at the high input amplitudes necessary for tissue liquefication. This, in turn, causes high stress concentrations at the node points, or points where the vibratory motion in the standing wave is zero. When stresses in vibratory elements are high, a material heating problem occurs. The temperature of the probe at the stressed node points elevates and the potential for tissue burning or charring exists. In a liposuction application, this phenomenon must be avoided, since the probes are inserted deeply into the body and burning could cause damage to the lower levels of the dermis, leading to scarring, infection, etc.
Accordingly, straight probes have not been proven particularly suitable for use in ultrasonic procedures even if the probes are adapted and tuned to resonate at the driving frequencies of the transducer system. U.S. Pat. No. 4,886,491 to Parisi et al., U.S. Pat. No. 5,123,903 to Quaid, and U.S. Pat. No. 5,419,761 to Alliger et al. all show typical embodiments for ultrasonic probes used in liposuction procedures. In practice, these probes have heated significantly at the nodal regions, been prone to fracture at higher vibratory amplitudes and have a tendency to break into transverse motion, wherein the tips of the probes whip, causing fracturing and the possibility of leaving pieces of metal in the operating field. Damage to the tissue not normally associated with a properly designed ultrasonic element may also occur. This fact is indirectly acknowledged in U.S. Pat. No. 4,886,491 which prescribes low amplitude vibrations of 2 mils peak-to-peak (50 microns pp). However, amplitudes in this range have been shown not to be adequate for liquefying certain fatty deposits of the body, especially those in the saddlebag areas.